In doing some more reading, I found where the FOM (8-12) says we must engage NAV by 500’ on RNAV SIDS. So the bold part below may not be accurate. (FOM applies to both aircraft, so we can negate the 200/900 CFM differences).
Originally Posted by
Lenticularis
Please show me where the book says HDG/NAV at 400ft? In fact the HDG/NAV must be selected before reaching 400ft and that is what people are confused over. The memo that someone is referencing spoke about this exact point. If NAV is needed it must be selected prior to 400 so that the proper lateral path may be flown for RNAV OFF RWY operations.